Display screen or portion thereof with transitional graphical user interface



FIG. 1 is the first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is the second image thereof;

FIG. 3 is the third image thereof;

FIG. 4 is the fourth image thereof;

FIG. 5 is the fifth image thereof;

FIG. 6 is the first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing an alternate embodiment of our new design;

FIG. 7 is the second image thereof;

FIG. 8 is the third image thereof;

FIG. 9 is the fourth image thereof;

FIG. 10 is the fifth image thereof;

FIG. 11 is the first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing another alternate embodiment of our new design;

FIG. 12 is the second image thereof;

FIG. 13 is the third image thereof;

FIG. 14 is the fourth image thereof; and,

FIG. 15 is the fifth image thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-5, 6-10, and 11-15. The process or period in which one image transitions to another image forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 